LEGUMINOUS CHOPS. 103 



over the whole period of 30 years, after the recent accumu- 

 lations had been worked out, the root-crops gave an average 

 of only 16.4 lb. of nitrogen per acre per annum. 



It is remarkable how very similar is the amount of Similarity 

 nitrogen annually accumulated in gramineous, cruciferous, lnammtr ^ 

 and chenopodiaceous crops, after the soil had been exhausted m grain 

 of the more recent and more readily available nitrogenous andr oot- 

 accumulations. Thus, over the second half of the period, the CT ° ps ' 

 wheat gave 17.2 lb., and the barley 18.8 lb., against 16.4 lb. 

 over 30 years in the various root-crops. 



We now come to the yield of nitrogen in leguminous crops. Yield of 

 Referring first to the results obtained with beans, it is seen n> itro 9 en *» 

 that over the first half of the period of 24 years, the average crops. 

 annual yield of nitrogen in the crop was 61.5 lb. per acre ; 

 whilst over the second 12 years — in 3 of which the crop 

 failed, so that there were only 9 years of beans, one of wheat, 

 and two of fallow — the annual yield was less than half as 

 much, or only 29.5 lb. per acre. Nevertheless, the average 

 yield over the 24 years without any nitrogenous manure, was 

 45.5 lb. per acre per annum. That is to say, under very 

 similar conditions as to soil-supply, the highly nitrogenous 

 leguminous crop, beans, has yielded over a given area twice 

 as much nitrogen as either wheat or barley, and more than 

 twice as much as the root-crops. 



The last results in the table relate to the leguminous crop Clover sfck- 

 — clover. It is well known that clover fails when it is ness ' ■ 

 attempted to grow it too frequently on the same land ; and, 

 in the case recorded in the table, it happened that clover was 

 obtained in only 6 years out of the 22 for which the yield of Yield of 

 nitrogen is given ; so that there are included, owing to the n itr ° aen 

 failures, 1 year of wheat, 3 of barley, and 12 of fallow. 

 Notwithstanding this, there was, with the occasional inter- 

 polation of the clover, an average yield over the 22 years of 

 39.8 lb. of nitrogen per acre with mineral, but without nitro- 

 genous supply. 



The next illustrations show more strikingly still the Yields of 

 greater yield of nitrogen in leguminous than in gramineous 7 l ltro 9f"' 

 crops, when grown under equal soil conditions. They relate and clover 

 to the yield of nitrogen in barley and in clover, grown side by compared. 

 side in the same field ; and the results are given in Table 33. 



The field had grown one crop of wheat, one of oats, and 

 three of barley in succession, with artificial mineral and nitro- 

 genous manures ; but without any farmyard or other organic 

 manure. In 1872 barley was again sown ; on one half alone, 

 and on the other half with clover. In 1873 barley was 

 again grown on the one half, but the clover on the other. 



